1. Field of the Invention
The present invention relates to an ink jet print head and an ink jet printing apparatus and more specifically to a technology that prevents warping and cracking of a heater substrate by alleviating stresses of a base plate forming the ink jet print head.
2. Description of the Related Art
In an ink jet system that heats ink by a heating resistor to eject an ink droplet, a substrate in which ejection energy generation devices are provided (hereinafter referred to as a “heater substrate”) is conventionally joined to a base plate of a different material from that of the heater substrate.
There is a construction in which a slit is provided at ends of an interface of the joint to alleviate stresses produced at the joint interface because of a difference in expansion coefficient between the heater substrate and the base plate as the temperature of the print head varies (see Japanese Patent Application Laid-open No. 2001-138528).
According to the method of the Japanese Patent Application Laid-open No. 2001-138528, however, there is no other alternative but to provide a slit at the ends of the joint interface, excluding a nozzle column, because of a physical structure of the base plate and a nozzle plate, with the result that stresses may develop at the joint interface in an area of the nozzle column due to the expansion coefficient difference.
Especially with an elongate print head that employs a thermal ink jet system and has a wide print width, there is a large temperature dynamic range. So, serious problems, such as warping and cracking of the print head may result.